The present invention relates to a cylinder head gasket installed between two members, such as a cylinder head and a cylinder block, of an internal combustion engine for sealing.
In case contacting surfaces of the cylinder head and the cylinder block (cylinder body) of an engine of an automobile are sealed, a cylinder head gasket made of metal is installed therebetween to seal combustion gas, cooling water and lubricating oil.
A cylinder head gasket has been changed from a lamination type formed of a plurality of metal plates laminated together to a simple type formed of one or two metal plates with a demand of lightening weight of an engine and reducing a manufacturing cost. Also, a material to be used as the gasket is limited and a kind and a number of sealing means are limited because of one or two metal plates as the constituting plates and lightening of the engine. It is thus required to use a relatively simple sealing means.
Also, as a result of lightening of the engine and making the engine small, rigidity of the engine is lowered. In sealing the cylinder head gasket, if a large sealing surface pressure is applied around a peripheral portion close to a cylinder bore in order to obtain a sealing ability, deformation of a cylinder bore with low rigidity is further promoted. Thus, the sealing means of the gasket can not function sufficiently, and it is difficult to obtain an appropriate sealing ability.
On the other hand, for example, as shown in FIG. 9, a metal laminate gasket 5 has been proposed such that in a metal cylinder head gasket 5 for an internal combustion engine formed of metal plates 60, 70 constituting at least two metal main bodies, one metal plate 60 is bent around a hole 6 to be sealed to form a sealing portion with a flange 61, at least one bead 61b is formed at the flange 61, and another metal plate 70 is laminated not to overlap an end portion 61c of the flange 61 (refer to Patent Document 1).
In this structure, a portion to be sealed can be sealed properly with thin plates and with a relatively lower tightening pressure, and when a force is applied to the gasket, the gasket can slide relatively easily with respect to a cylinder head contacting the gasket. Also, it is possible to provide a relatively large sealing area around a hole to be sealed.
However, in the structure disclosed in the metal laminate gasket, since the bead formed at the flange-projects inwardly, a large sealing surface pressure is not generated. Also, since a portion outside the bead extends in an annular shape, a surface pressure distribution concentrically formed is prevented. In the gasket 5 as shown in FIG. 9, the surface pressure distribution appears as shown in FIG. 10. Accordingly, it may not properly respond to sealing requirement of a cylinder bore of an engine with small size and low rigidity.
Patent Document: Japanese Utility Model Publication (Kokai) No. 3-19452.
The present invention has been made in view of the above problems, and an object of the invention is to provide a cylinder head gasket which can provide sufficient sealing ability while preventing deformation of a cylinder bore of an engine.
Further objects and advantages of the invention will be apparent from the following description of the invention.